So the Chevelle headers do not fit to my liking. The passenger side would have a problem with the front driveshaft if the suspension were to hit the bump stops. Going to full static articulation (lifting the front passenger wheel until the rear passenger wheel begins to lift), I still had enough room for a wrench to fit between the driveshaft and one of the header primary tubes. But with more than an inch left before the spring would hit either of the two bump stops, I decided to play it safe and get the proper headers.
I was able to get a set of Hooker headers for $146 delivered next day from Amazon.com. The headers and the exhaust system I have purchased are made to work with each other nicely. However, not as nice as a true bolt in. Some "massaging" of the exhaust will be necessary to get the mufflers and tail pipes located where I want them. Nothing a cutoff wheel and a welder will not fix.
The good news is that I was able to save the Flowmaster Series 40 mufflers that were on the truck and they will get welded back into the system. I am trying to find some high temp cold galvanizing paint locally right now so I can spray down the welds to try and prohibit rust formation.
I also did some more digging into the speedometer calibration and what needed to be done. I pulled the driven gear out of the back of the transfer case and had a look at it. It has a 7 tooth drive gear and a 19 tooth driven gear. I would need to step up to a 23 tooth driven gear to get the speedo to read right. However, only up to a 21 tooth gear is available. So I will need to purchase an add-on unit (speedometer ratio adapter) to get to the proper ratio.
I have pictures of all of this stuff, but will have to update later.